Mineralogical characterization of rejuvenated magmatism at Burton Guyot, Louisville Seamount trail

Volcaniclastic sequences drilled during IODP Expedition 330 on top of Burton Guyot preserve a unique record of rejuvenated magmatic activity along the Louisville Seamount trail. Geochemical analysis of clinopyroxenes in primary volcaniclastic deposits of this rejuvenated phase allows the reconstruction of magmatic evolution from the shield to post-erosional phases of a Louisville seamount, and to compare this evolution to that of Hawaiian volcanoes. Our results reveal the occurrence of three main types of clinopyroxenes in the rejuvenated volcaniclastic deposits at Burton Guyot, with a Na (and Al)-poor phenocrystic clinopyroxene and two types of Na-rich clinopyroxenes from disaggregated ultramafic xenoliths. The rejuvenated Na-poor phenocrysts have the same compositional range as clinopyroxenes associated with the shield stage of the volcano, indicating an overlap in shield and rejuvenated magma compositions. The dominant type of Na-rich clinopyroxene (Type 1) is very similar to clinopyroxenes in Hawaiian pyroxenitic xenoliths thought to represent high pressure cumulates. Their relatively low Mg/(Mg + Fe), Cr, and Sc contents, similar trace element abundances and high Al(vi):Al(iv) to Hawaiian cumulates indicates that they too are cumulates. This contrasts with lower Al(vi):Al(iv) of the Na-poor phenocrysts that crystallized between 6–7 kbars and 1150–1200 °C. Type 2 clinopyroxenes are Mg-rich, and have major and trace element compositions very similar to clinopyroxenes in Hawaiian peridotites. These clinopyroxenes are interpreted as fragments of mantle xenoliths. They show intermediate amounts of incompatible element depletion, between more enriched Hawaiian peridotites and strongly depleted abyssal peridotites. Some grains exhibit the effects of mantle metasomatism, having spoon-shaped, chondrite-normalized REE patterns like those of Hawaiian peridotite xenoliths. The occurrence of disaggregated pyroxenitic cumulates and metasomatized mantle xenoliths in rejuvenated magmas of both Burton Guyot and Hawaiian islands suggests that the plumbing system of these volcanic systems share significant similarities. However, consistently with previous geochemical studies of the Louisville seamounts, geochemical consistency of shield and rejuvenated clinopyroxenes at Burton Guyot show that this volcano experienced similar alkaline magmatism from shield to rejuvenated stages. This is an important difference with the evolution of Hawaiian volcanoes that includes a dominantly tholeiitic shield stages and alkaline post-shield and rejuvenated stages, which suggests that the model of Hawaiian island formation may not be fully applicable to Louisville seamounts

Louisville Seamount Trail: implications for geodynamic mantle flow models and the geochemical evolution of primary hotspots

The Louisville Seamount Trail is a 4300 km long volcanic chain that has been built in the past 80 m.y. as the Pacific plate moved over a persistent mantle melting anomaly or hotspot. Because of its linear morphology and its long-lived age-progressive volcanism, Louisville is the South Pacific counterpart of the much better studied Hawaiian-Emperor Seamount Trail. Together, Louisville and Hawaii are textbook examples of two primary hotspots that have been keystones in deciphering the motion of the Pacific plate relative to a set of "fixed" deep-mantle plumes. However, drilling during Ocean Drilling Program (ODP) Leg 197 in the Emperor Seamounts documented a large ~15° southward motion of the Hawaiian hotspot prior to 50 Ma. Is it possible that the Hawaiian and Louisville hotspots moved in concert and thus constitute a moving reference frame for modeling plate motion in the Pacific? Alternatively, could they have moved independently, as predicted by mantle flow models that reproduce the observed latitudinal motion for Hawaii but that predict a largely longitudinal shift for the Louisville hotspot? These two end-member geodynamic models were tested during Integrated Ocean Drilling Program (IODP) Expedition 330 to the Louisville Seamount Trail. In addition, existing data from dredged lavas suggest that the mantle plume source of the Louisville hotspot has been remarkably homogeneous for as long as 80 m.y. These lavas are predominantly alkali basalts and likely represent a mostly alkalic shield-building stage, which is in sharp contrast to the massive tholeiitic shield-building stage of Hawaiian volcanoes. Geochemical and isotopic data for the recovered lavas during Expedition 330 will provide insights into the magmatic evolution and melting processes of individual Louisville volcanoes, their progression from shield-building to postshield and (maybe) posterosional stages, the temperature and depth of partial melting of their mantle plume source, and the enigmatic long-lived and apparent geochemical homogeneity of the Louisville mantle source. Collectively, this will enable us to characterize the Louisville Seamount Trail as a product of one of the few global primary hotspots, to better constrain its plume-lithosphere interactions, and to further test the hypothesis that the Ontong Java Plateau formed from the plume head of the Louisville mantle plume around 120 Ma. During Expedition 330 we replicated the drilling strategy of Leg 197, the first expedition to provide compelling evidence for the motion of the Hawaiian mantle plume between 80 and 50 Ma. For that reason we targeted Louisville seamounts that have ages similar to Detroit, Suiko, Nintoku, and Koko Seamounts in the Emperor Seamount Trail. In total, five seamounts were drilled in the Louisville Seamount Trail: Canopus, Rigil, Burton, Achernar, and Hadar Guyots (old to young). By analyzing a large number of time-independent in situ lava flows (and other volcanic eruptive products) from these seamounts using modern paleomagnetic, 40Ar/39Ar geochronological, and geochemical techniques, we will be able to directly compare the paleolatitude estimates and geochemical signatures between the two longest-lived hotspot systems in the Pacific Ocean. We drilled into the summits of the five Louisville guyots and reached volcanic basement at four of these drilling targets. In two cases we targeted larger seamount structures and drilled near the flanks of these ancient volcanoes, and in the other three cases we selected smaller edifices that we drilled closer to their centers. Drilling and logging plans for each of these sites were similar, with coring reaching 522.0 meters below seafloor (mbsf) for Site U1374 and 232.9, 65.7, 11.5, 182.8, and 53.3 mbsf for Sites U1372, U1373, U1375, U1376, and U1377, respectively. Some Expedition 330 drill sites were capped with only a thin layer of pelagic ooze between 6.6 and 13.5 m thick, and, if present, these were cored by using a low-rotation gravity-push technique with the rotary core barrel to maximize recovery. However, at Sites U1373 and U1376 no pelagic ooze was present, and the holes needed to be started directly into cobble-rich hardgrounds. In all cases, the bulk of the seamount sediment cover comprised sequences of volcanic sandstones and various kinds of basalt breccia or basalt conglomerate, which often were interspersed with basaltic lava flows, the spatter/tephra products of submarine eruptions, or other volcanic products, including auto-brecciated flows or peperites. Also several intervals of carbonate were cored, with the special occurrence of a ~15 m thick algal limestone reef at Site U1376 on Burton Guyot. In addition, some condensed pelagic limestone units were recovered on three of the other seamounts, but these did not exceed 30 cm in thickness. Despite their limited presence in the drilled sediment, these limestones provide valuable insights for the paleoclimate record at high ~50° southern latitudes since Mesozoic times. Several Louisville sites progressed from subaerial conditions in the top of volcanic basement into submarine eruptive environments, or drilling of the igneous basement immediately started in submarine volcanic sequences, as was the case for Sites U1376 and U1377 on Burton and Hadar Guyots. At three sites we cored >100 m into the igneous basement: 187.3 m at Site U1372, 505.3 m at Site U1374, and 140.9 m at Site U1376. At the other sites we did not core into basement (Site U1375) or we cored only 38.2 m (Site U1377) because of unstable hole conditions. Even so, drilling during Expedition 330 resulted in a large number of in situ lava flows, pillow basalts, or other types of volcanic products such as auto-brecciated lava flows, intrusive sheets or dikes, and peperites. In particular, the three holes on Canopus and Rigil Guyots (the two oldest seamounts drilled in the Louisville Seamount Trail), resulted in adequate numbers of in situ lava flows to average out paleosecular variation, with probable eruption ages estimated at ~78 and 73 Ma, respectively. Remarkably, at all drill sites large quantities of hyaloclastites, volcanic sandstones, and basaltic breccias were also recovered, which in many cases show consistent paleomagnetic inclinations compared to the lava flows bracketing these units. For Site U1374 on Rigil Guyot we also observed a magnetic polarity reversal in the cored sequence. Overall, this is very promising for determining a reliable paleolatitude record for the Louisville Seamounts following detailed postcruise examinations. The deeper penetrations of several hundred meters required bit changes and reentries using free-fall funnels. Basement penetration rates were 1.8–2.5 m/h depending on drill depth. In total, 1114 m of sediment and igneous basement at five seamounts was drilled, and 806 m was recovered (average recovery = 72.4%). At Site U1374 on Rigil Guyot, a total of 522 m was drilled, with a record-breaking 87.8% recovery. Most outstandingly, nearly all Expedition 330 core material is characterized by low degrees of alteration, providing us with a large quantity of samples of mostly well-preserved basalt, containing, for example, pristine olivine crystals with melt inclusions, fresh volcanic glass, unaltered plagioclase, carbonate, zeolite and celadonite alteration minerals, various micro- and macrofossils, and, in one case, mantle xenoliths and xenocrysts. The large quantity and excellent quality of the recovered sample material allow us to address all the scientific objectives of this expedition and beyond

Parents' experiences of their child's disclosure of sexual abuse

A child’s disclosure of sexual victimisation is a difficult experience for parents, and has been associated with traumatisation, disbelief, denial, self-blame and clinical difficulties. To date, most studies on parents’ responses have been quantitative assessments of the psychological impact of disclosure on parents. A paucity of research has qualitatively explored mothers’ experiences of their child’s disclosure of child sexual abuse (CSA) and fathers’ experiences have been even further neglected. The current study seeks to characterise parents’ experiences of their child’s disclosure of CSA and to uncover the process-oriented nature of parental responses. This qualitative study, using a grounded theory approach to analysis, involved interviews with 10 mothers and four fathers, whose children (3 to 18 years) had experienced sexual abuse. Three themes emerged from the analysis. The first theme – making sense of the abuse in retrospect – captured the process through which parents sought to make sense of their child’s disclosure, focusing on why their child had not disclosed the abuse to them earlier, and how they had noticed something was wrong but misattributed their child’s behaviour to other factors. The second theme – negotiating parental identity as protector – reflected how parents’ identity as a protector was challenged, their perception of their world had been forever altered, and they now experienced themselves as hypervigilant and overprotective. The final theme - navigating the services – pertained to parents’ struggle in navigating child protection and police services, and feeling of being isolated and alone. These findings highlight the need for empathy and parental support following child disclosure of sexual victimisation

Queer Youth and the Culture Wars: From Classroom to Courtroom in Australia, Canada and the United States

This article builds on Lugg\u27s (2006) discussion of surveillance in public schools and how queer youth are resisting schools\u27 current efforts to regulate sexual orientation and gender expression in the U.S. and internationally. Legal complaints initiated by queer youth against their schools for harassment and access to extra-curricular activities are discussed. The number of cases in the past five years has increased significantly and the courts are siding with the youth and their allies, demonstrating that queer youth are significantly impacting the dismantling of heteronormative regulatory regimes and improving the school experiences for themselves and queer adults

Choice-Disability and HIV Infection: A Cross Sectional Study of HIV Status in Botswana, Namibia and Swaziland

Interpersonal power gradients may prevent people implementing HIV prevention decisions. Among 7,464 youth aged 15–29 years in Botswana, Namibia and Swaziland we documented indicators of choice-disability (low education, educational disparity with partner, experience of sexual violence, experience of intimate partner violence (IPV), poverty, partner income disparity, willingness to have sex without a condom despite believing partner at risk of HIV), and risk behaviours like inconsistent use of condoms and multiple partners. In Botswana, Namibia and Swaziland, 22.9, 9.1, and 26.1% women, and 8.3, 2.8, and 9.3% men, were HIV positive. Among both women and men, experience of IPV, IPV interacted with age, and partner income disparity interacted with age were associated with HIV positivity in multivariate analysis. Additional factors were low education (for women) and poverty (for men). Choice disability may be an important driver of the AIDS epidemic. New strategies are needed that favour the choice-disabled

Identification of Loci Controlling Restriction of Parasite Growth in Experimental Taenia crassiceps Cysticercosis

Human neurocysticercosis (NC) caused by Taenia solium is a parasitic disease of the central nervous system that is endemic in many developing countries. In this study, a genetic approach using the murine intraperitoneal cysticercosis caused by the related cestode Taenia crassiceps was employed to identify host factors that regulate the establishment and proliferation of the parasite. A/J mice are permissive to T. crassiceps infection while C57BL/6J mice (B6) are comparatively restrictive, with a 10-fold difference in numbers of peritoneal cysticerci recovered 30 days after infection. The genetic basis of this inter-strain difference was explored using 34 AcB/BcA recombinant congenic strains derived from A/J and B6 progenitors, that were phenotyped for T. crassiceps replication. In agreement with their genetic background, most AcB strains (A/J-derived) were found to be permissive to infection while most BcA strains (B6-derived) were restrictive with the exception of a few discordant strains, together suggesting a possible simple genetic control. Initial haplotype association mapping using >1200 informative SNPs pointed to linkages on chromosomes 2 (proximal) and 6 as controlling parasite replication in the AcB/BcA panel. Additional linkage analysis by genome scan in informative [AcB55xDBA/2]F1 and F2 mice (derived from the discordant AcB55 strain), confirmed the effect of chromosome 2 on parasite replication, and further delineated a major locus (LOD = 4.76, p<0.01; peak marker D2Mit295, 29.7 Mb) that we designate Tccr1 (T. crassiceps cysticercosis restrictive locus 1). Resistance alleles at Tccr1 are derived from AcB55 and are inherited in a dominant fashion. Scrutiny of the minimal genetic interval reveals overlap of Tccr1 with other host resistance loci mapped to this region, most notably the defective Hc/C5 allele which segregates both in the AcB/BcA set and in the AcB55xDBA/2 cross. These results strongly suggest that the complement component 5 (C5) plays a critical role in early protective inflammatory response to infection with T. crassiceps